Pixel unit of electrochromic display panel and driving method thereof

ABSTRACT

A pixel unit of an electrochromic display panel and a driving method thereof are described. The pixel unit includes a first substrate; a first electrode and a second electrode, on the first substrate; a first auxiliary counter electrode, on the first substrate and disposed between the first electrode and the second electrode; a first electrochromic material, on the first electrode; a second electrochromic material, on the second electrode; a second substrate, opposite to the first substrate; a third electrode, on the second substrate; a third electrochromic material, on the third electrode; and an electrolyte layer, between the first substrate and the second substrate.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the priority benefit of Taiwan applicationserial no. 99146624, filed Dec. 29, 2010. The entirety of theabove-mentioned patent application is hereby incorporated by referenceherein and made a part of this specification.

TECHNICAL FIELD

The disclosure relates to a pixel unit of an electrochromic displaypanel and a driving method thereof.

BACKGROUND

The development of color electronic books has always been the focus ofmany industries, but existing color electronic books have a commonproblem of insufficient reflectivity. In a reflective display panel, twonoticeable technologies are used: one is an electrochromic displaytechnology, and the other is a cholesteric liquid crystal displaytechnology.

In a cholesteric liquid crystal display panel, since a cholestericliquid crystal can only reflect light of a single polarization state(for example, left-polarized light or right-polarized light), thereflectivity of the cholesteric liquid crystal display panel isphysically limited. In addition, in order to achieve a color cholestericliquid crystal display panel, a plurality of red, green, and bluesub-pixel areas is used for presentation. However, the reflectivity ofthe cholesteric liquid crystal display panel is further decreasedaccordingly, thus resulting in poor color display and low contrast.

In an electrochromic display panel, diverse colors may be displayed, andthe reflectivity may approach that of paper, so that the electrochromicdisplay technology is a promising display technology. Currently, manymaterial suppliers and academic research institutes have invested in thedevelopment, and it is believed that in the future, the switching rateand service life of the electrochromic display panel will be improvedsubstantially.

SUMMARY

An embodiment of the disclosure provides a pixel unit of anelectrochromic display panel, which includes a first substrate; a firstelectrode and a second electrode, on the first substrate; a firstauxiliary counter electrode, on the first substrate and disposed betweenthe first electrode and the second electrode; a first electrochromicmaterial, on the first electrode; a second electrochromic material, onthe second electrode; a second substrate, opposite to the firstsubstrate; a third electrode, on the second substrate; a thirdelectrochromic material, on the third electrode; and an electrolytelayer, between the first substrate and the second substrate.

An embodiment of the disclosure provides a method for driving the abovepixel unit of an electrochromic display panel, including the followingsteps. When a first voltage is applied to the first electrode and thesecond electrode, a second voltage is applied to the third electrode,and a third voltage is applied to the first auxiliary counter electrode,the pixel unit displays black as viewed from the top or the bottom ofthe pixel unit. When the first voltage is applied to the thirdelectrode, the second voltage is applied to the first auxiliary counterelectrode, and the third voltage is applied to the first electrode andthe second electrode, the pixel unit displays white as viewed from thetop or the bottom of the pixel unit. When the first voltage is appliedto the third electrode, the second voltage is applied to the firstelectrode and the second electrode, and the third voltage is applied tothe first auxiliary counter electrode, the pixel unit displays a firstcolor as viewed from the top or the bottom of the pixel unit. When thefirst voltage is applied to the first electrode and the secondelectrode, the second voltage is applied to the first auxiliary counterelectrode, and the third voltage is applied to the third electrode, thepixel unit displays a second color as viewed from the top or the bottomof the pixel unit. When the first voltage is applied to the firstauxiliary counter electrode, the second voltage is applied to the thirdelectrode, and the third voltage is applied to the first electrode andthe second electrode, the pixel unit displays a third color as viewedfrom the top or the bottom of the pixel unit.

Several exemplary embodiments accompanied with figures are described indetail below to further describe the disclosure in details.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are included to provide further understanding,and are incorporated in and constitute a part of this specification. Thedrawings illustrate exemplary embodiments and, together with thedescription, serve to explain the principles of the disclosure.

FIG. 1 is a schematic sectional view of a pixel unit of anelectrochromic display panel according to an embodiment of thedisclosure.

FIG. 2 is a schematic sectional view of a pixel unit of anelectrochromic display panel according to another embodiment of thedisclosure.

FIGS. 3 to 7 are schematic views of a driving method of a pixel unit ofan electrochromic display panel according to an embodiment of thedisclosure.

FIGS. 8 to 15 are schematic views of a driving method of a pixel unit ofan electrochromic display panel according to another embodiment of thedisclosure.

DETAILED DESCRIPTION OF DISCLOSED EMBODIMENTS Pixel Unit

FIG. 1 is a schematic sectional view of a pixel unit of anelectrochromic display panel according to an embodiment of thedisclosure. Referring to FIG. 1, a pixel unit of an electrochromicdisplay panel of this embodiment includes a first substrate 100, a firstelectrode 102, a second electrode 104, a first auxiliary counterelectrode 106, a first electrochromic material 112, a secondelectrochromic material 114, a second substrate 200, a third electrode202, and a third electrochromic material 212.

The first substrate 100 is mainly used for supporting devices and filmlayers. The second substrate 200 is opposite to the first substrate 100,and is also used for supporting devices and film layers. The firstsubstrate 100 and the second substrate 200 may be rigid substrates orflexible substrates. In addition, the first substrate 100 and the secondsubstrate 200 may be transparent substrates or reflective substrates(when reflective substrates are used, no reflective layer may beneeded), which are made of glass, silicon, metal, high polymer, or othersuitable materials. It should be noted that, both the first substrate100 and the second substrate 200 may be transparent substrates, or oneof the first substrate 100 and the second substrate 200 is a reflectivesubstrate. In addition, an electrolyte layer 300 is between the firstsubstrate 100 and the second substrate 200, and may be a polar liquidincluding water and metal salts dissolved in water, or including a polarsolvent and metal salts dissolved in the polar solvent.

The first electrode 102 and the second electrode 104 are on the firstsubstrate 100, and the first electrode 102 and the second electrode 104are electrically insulated from each other. In addition, the thirdelectrode 202 is on the second substrate 200. According to thisembodiment, the third electrode 202 is disposed above the firstelectrode 102 and the second electrode 104. In other words, an area ofthe third electrode 202 covers an area of the first electrode 102 andthe second electrode 104. Here, the first electrode 102, the secondelectrode 104, and the third electrode 202 may independently be atransparent electrode or a reflective electrode. The transparentelectrode may be made of a metal oxide, for example, indium tin oxide,indium zinc oxide, aluminum tin oxide, aluminum zinc oxide, indiumgallium zinc oxide, or other suitable materials. The reflectiveelectrode is made of, for example, metal. According an embodiment, ifthe first electrode 102, the second electrode 104, and the thirdelectrode 202 are all transparent electrodes, one of the first substrate100 and the second substrate 200 is a reflective substrate. When thefirst substrate 100 is a reflective substrate, a viewer has to view ascreen from the second substrate 200, that is, look down from the top ofFIG. 1. When the second substrate 200 is a reflective substrate, theviewer has to view the screen from the first substrate 100, that is,look up from the bottom of FIG. 1. According to another embodiment, thefirst electrode 102 and the second electrode 104 are reflectiveelectrodes, and the third electrode 202 is a transparent electrode, andin this case, the viewing direction of the viewer is from top to bottom.According to still another embodiment, the first electrode 102 and thesecond electrode 104 are transparent electrodes, and the third electrode202 is a reflective electrode, and in this case, the viewing directionof the viewer is from bottom to top.

In addition, the first auxiliary counter electrode 106 is on the firstsubstrate 100, and is disposed between the first electrode 102 and thesecond electrode 104. The first auxiliary counter electrode 106 iselectrically insulated from the first electrode 102, and the firstauxiliary counter electrode 106 is also electrically insulated from thesecond electrode 104. According to this embodiment, a shading pattern116 may be further disposed on the first auxiliary counter electrode106. However, in another embodiment, the shading pattern 116 may not beincluded.

In addition, the first electrochromic material 112 is on the firstelectrode 102. The second electrochromic material 114 is on the secondelectrode 104. The third electrochromic material 212 is on the thirdelectrode 202. According to this embodiment, the third electrochromicmaterial 212 is above the first electrochromic material 112 and thesecond electrochromic material 114. In other words, an area of the thirdelectrochromic material 212 covers an area of the first electrochromicmaterial 112 and the second electrochromic material 114.

Here, one of the first electrochromic material 112, the secondelectrochromic material 114, and the third electrochromic material 212is a monochromatic-transparent electrochromic material, and the othertwo are a dichromatic-transparent electrochromic material. Preferably,the first electrochromic material 112 and the second electrochromicmaterial 114 are a dichromatic-transparent electrochromic material, andthe third electrochromic material 212 is a monochromatic-transparentelectrochromic material. Generally, the monochromatic-transparentelectrochromic material refers to a material which can switch between asingle color and transparent according to a driving voltage. Forexample, when a reduction voltage is applied to an electrode of themonochromatic-transparent electrochromic material, themonochromatic-transparent electrochromic material may be colored to bered (R); and when no voltage is applied to the electrode of themonochromatic-transparent electrochromic material, themonochromatic-transparent electrochromic material may be decolored to betransparent (T). In addition, the dichromatic-transparent electrochromicmaterial refers to a material which can switch between two colors andtransparent according to a driving voltage. For example, when areduction voltage is applied to an electrode of thedichromatic-transparent electrochromic material, thedichromatic-transparent electrochromic material may be colored to begreen (G); when an oxidation voltage is applied to the electrode of thedichromatic-transparent electrochromic material, thedichromatic-transparent electrochromic material may be colored to beblue (B); and when no voltage is applied to the dichromatic-transparentelectrochromic material, the dichromatic-transparent electrochromicmaterial may be decolored to be transparent (T).

The monochromatic-transparent electrochromic material may be selectedfrom a blue-transparent (B-T) electrochromic material, agreen-transparent (G-T) electrochromic material, or a red-transparent(R-T) electrochromic material. The dichromatic-transparentelectrochromic material may be selected from a blue-green-transparent(B-G-T) electrochromic material, a green-red-transparent (G-R-T)electrochromic material, or a red-blue-transparent (R-B-T)electrochromic material. In order to enable the pixel unit to presentred, green, and blue, the first electrochromic material 112, the secondelectrochromic material 114, and the third electrochromic material 212are preferably selected from electrochromic materials covering red,green, and blue. For example, the first electrochromic material 112 andthe second electrochromic material 114 are the B-G-T electrochromicmaterial, and the third electrochromic material 212 is the R-Telectrochromic material.

FIG. 2 is a schematic sectional view of a pixel unit of anelectrochromic display panel according to another embodiment of thedisclosure. Since the embodiment of FIG. 2 is similar to that of FIG. 1,elements in FIG. 2 that are the same as those in FIG. 1 are representedby the same symbols, and are not repeated again. The difference betweenthe embodiment of FIG. 2 and that of FIG. 1 lies in that, the embodimentof FIG. 2 further includes a fourth electrode 204, a fourthelectrochromic material 214, and a second auxiliary counter electrode206.

The fourth electrode 204 is on the second substrate 200, and iselectrically insulated from the third electrode 202. Here, the thirdelectrode 202 is correspondingly disposed above the first electrode 102,and the fourth electrode 204 is correspondingly disposed above thesecond electrode 104. The fourth electrode 204 may be a transparentelectrode or a reflective electrode, and may be made of a material asthat of the first, second, and third electrodes. If the third electrode202 is a transparent electrode, the fourth electrode 204 is also atransparent electrode, and in this case the viewing direction of theviewer is from top to bottom. If the third electrode 202 is a reflectiveelectrode, the fourth electrode 204 is also a reflective electrode, andin this case the viewing direction of the viewer is from bottom to top.

The second auxiliary counter electrode 206 is on the second substrate200, and is disposed between the third electrode 202 and the fourthelectrode 204. The second auxiliary counter electrode 206 iselectrically insulated from the third electrode 202, and the secondauxiliary counter electrode 206 is also electrically insulated from thefourth electrode 204. According to this embodiment, a shading pattern216 may be further disposed on the second auxiliary counter electrode206. However, in another embodiment, the shading pattern 216 may not beincluded.

The fourth electrochromic material 214 is on the fourth electrode 204.Here, two of the first electrochromic material 112, the secondelectrochromic material 114, the third electrochromic material 212, andthe fourth electrochromic material 214 are a monochromatic-transparentelectrochromic material, and the other two are a dichromatic-transparentelectro chromic material. Similarly, the monochromatic-transparentelectrochromic material may be selected from a B-T electrochromicmaterial, a G-T electrochromic material, or an R-T electrochromicmaterial. The dichromatic-transparent electrochromic material may beselected from a B-G-T electrochromic material, a G-R-T electrochromicmaterial, or an R-B-T electrochromic material. In order to enable thepixel unit to present red, green, blue, and other colors, the firstelectrochromic material 112, the second electrochromic material 114, thethird electrochromic material 212, and the fourth electrochromicmaterial 214 are preferably selected from electrochromic materialscovering red, green, and blue. For example, the first electrochromicmaterial 112 and the second electrochromic material 114 are the B-G-Telectrochromic material, and the third electrochromic material 212 andthe fourth electrochromic material 214 are the R-T electrochromicmaterial.

Driving Method

FIGS. 3 to 7 are schematic views of a driving method of a pixel unit ofan electrochromic display panel according to an embodiment of thedisclosure. Specifically, FIGS. 3 to 7 show a driving methodcorresponding to the pixel unit of an electrochromic display panel ofFIG. 1. In order to illustrate in detail color display of the pixel unitof this embodiment, an example is taken, in which the firstelectrochromic material 112 and the second electrochromic material 114of this embodiment are the B-G-T dichromatic electrochromic material,and the third electrochromic material 212 of this embodiment is the R-Tmonochromatic electrochromic material. However, the disclosure is notlimited thereto. In other words, in other embodiments, the firstelectrochromic material 112, the second electrochromic material 114, andthe third electrochromic material 212 may be combinations of otherelectrochromic materials.

Referring to FIG. 3, if the pixel unit is to display black, a firstvoltage V1 (for example, a reduction voltage) is applied to the firstelectrode 102 and the second electrode 104, a second voltage V2 (forexample, an oxidation voltage) is applied to the third electrode 202,and a third voltage V3 (for example, a zero voltage) is applied to thefirst auxiliary counter electrode 106. In this case, since the firstelectrode 102 and the second electrode 104 are at a reduction potential,the third electrode 202 is at an oxidation potential, and the firstauxiliary counter electrode 106 is in an open circuit state, electriccurrents (as indicated by arrows) flow from the first electrode 102 andthe second electrode 104 to the third electrode 202. As such, the firstelectrochromic material 112 and the second electrochromic material 114are colored to be green (G), and the third electrochromic material 212is colored to be red (R). Therefore, in this case the pixel unitpresents black when viewed from the top or the bottom of the pixel unit.

Referring to FIG. 4, if the pixel unit is to display white, the firstvoltage V1 (for example, the reduction voltage) is applied to the thirdelectrode 202, the second voltage V2 (for example, the oxidationvoltage) is applied to the first auxiliary counter electrode 106, andthe third voltage V3 (for example, the zero voltage) is applied to thefirst electrode 102 and the second electrode 104. In this case, sincethe third electrode 202 is at the reduction potential, the firstauxiliary counter electrode 106 is at the oxidation potential, and thefirst electrode 102 and the second electrode 104 are in an open circuitstate, electric currents (as indicated by arrows) flow from the thirdelectrode 202 to the first auxiliary counter electrode 106. As such, thefirst electrochromic material 112, the second electrochromic material114, and the third electrochromic material 212 are all decolored to betransparent (T). Therefore, in this case the pixel unit presents whitewhen viewed from the top or the bottom of the pixel unit.

Referring to FIG. 5, if the pixel unit is to display blue, the firstvoltage V1 (for example, the reduction voltage) is applied to the thirdelectrode 202, the second voltage V2 (for example, the oxidationvoltage) is applied to the first electrode 102 and the second electrode104, and the third voltage V3 (for example, the zero voltage) is appliedto the first auxiliary counter electrode 106. In this case, since thethird electrode 202 is at the reduction potential, the first electrode102 and the second electrode 104 are at the oxidation potential, and thefirst auxiliary counter electrode 106 is in an open circuit state,electric currents (as indicated by arrows) flow from the third electrode202 to the first electrode 102 and the second electrode 104. As such,the first electrochromic material 112 and the second electrochromicmaterial 114 are colored to be blue (B), and the third electrochromicmaterial 212 is decolored to be transparent (T). Therefore, in this casethe pixel unit presents blue when viewed from the top or the bottom ofthe pixel unit.

Referring to FIG. 6, if the pixel unit is to display green, the firstvoltage V1 (for example, the reduction voltage) is applied to the firstelectrode 102 and the second electrode 104, the second voltage V2 (forexample, the oxidation voltage) is applied to the first auxiliarycounter electrode 106, and the third voltage V3 (for example, the zerovoltage) is applied to the third electrode 202. In this case, since thefirst electrode 102 and the second electrode 104 are at the reductionpotential, the first auxiliary counter electrode 106 is at the oxidationpotential, and the third electrode 202 is in an open circuit state,electric currents (as indicated by arrows) flow from the first electrode102 and the second electrode 104 to the first auxiliary counterelectrode 106. As such, the first electrochromic material 112 and thesecond electrochromic material 114 are colored to be green (G), and thethird electrochromic material 212 is decolored to be transparent (T).Therefore, in this case the pixel unit presents green when viewed fromthe top or the bottom of the pixel unit.

Referring to FIG. 7, if the pixel unit is to display red, the firstvoltage V1 (for example, the reduction voltage) is applied to the firstauxiliary counter electrode 106, the second voltage V2 (for example, theoxidation voltage) is applied to the third electrode 202, and the thirdvoltage V3 (for example, the zero voltage) is applied to the firstelectrode 102 and the second electrode 104. In this case, since thefirst auxiliary counter electrode 106 is at the reduction potential, thethird electrode 202 is at the oxidation potential, and the firstelectrode 102 and the second electrode 104 are in an open circuit state,electric currents (as indicated by arrows) flow from the first auxiliarycounter electrode 106 to the third electrode 202. As such, the firstelectrochromic material 112 and the second electrochromic material 114are decolored to be transparent (T), and the third electrochromicmaterial 212 is colored to be red (R). Therefore, in this case the pixelunit presents red when viewed from the top or the bottom of the pixelunit.

FIGS. 8 to 15 are schematic views of a driving method of a pixel unit ofan electrochromic display panel according to another embodiment of thedisclosure. Specifically, FIGS. 8 to 15 show a driving methodcorresponding to the pixel unit of an electrochromic display panel ofFIG. 2. In order to illustrate in detail color display of the pixel unitof this embodiment, an example is taken, in which the firstelectrochromic material 112 and the second electrochromic material 114of this embodiment are the B-G-T dichromatic electrochromic material,and the third electrochromic material 212 and the fourth electrochromicmaterial 214 of this embodiment are the R-T monochromatic electrochromicmaterial. However, the disclosure is not limited thereto. In otherwords, in other embodiments, the first electrochromic material 112, thesecond electrochromic material 114, the third electrochromic material212, and the fourth electrochromic material 214 may be combinations ofother electrochromic materials.

Referring to FIG. 8, if the pixel unit is to display black, the firstvoltage V1 (for example, the reduction voltage) is applied to the firstelectrode 102 and the second electrode 104, the second voltage V2 (forexample, the oxidation voltage) is applied to the third electrode 202and the fourth electrode 204, and the third voltage V3 (for example, thezero voltage) is applied to the first auxiliary counter electrode 106and the second auxiliary counter electrode 206. In this case, since thefirst electrode 102 and the second electrode 104 are at the reductionpotential, the third electrode 202 and the fourth electrode 204 are atthe oxidation potential, and the first auxiliary counter electrode 106and the second auxiliary counter electrode 206 are in an open circuitstate, electric currents (as indicated by arrows) flow from the firstelectrode 102 and the second electrode 104 to the third electrode 202and the fourth electrode 204. As such, the first electrochromic material112 and the second electrochromic material 114 are colored to be green(G), and the third electrochromic material 212 and the fourthelectrochromic material 214 are colored to be red (R). Therefore, inthis case the pixel unit presents black when viewed from the top or thebottom of the pixel unit.

Referring to FIG. 9, if the pixel unit is to display white, the firstvoltage V1 (for example, the reduction voltage) is applied to the thirdelectrode 202 and the fourth electrode 204, the second voltage V2 (forexample, the oxidation voltage) is applied to the first auxiliarycounter electrode 106, and the third voltage V3 (for example, the zerovoltage) is applied to the first electrode 102, the second electrode104, and the second auxiliary counter electrode 206. In this case, sincethe third electrode 202 and the fourth electrode 204 are at thereduction potential, the first auxiliary counter electrode 106 is at theoxidation potential, and the first electrode 102, the second electrode104, and the second auxiliary counter electrode 206 are in an opencircuit state, electric currents (as indicated by arrows) flow from thethird electrode 202 and the fourth electrode 204 to the first auxiliarycounter electrode 106. As such, the first electrochromic material 112,the second electrochromic material 114, the third electrochromicmaterial 212, and the fourth electrochromic material 214 are alldecolored to be transparent (T). Therefore, in this case the pixel unitpresents white when viewed from the top or the bottom of the pixel unit.

Referring to FIG. 10, if the pixel unit is to display blue, the firstvoltage V1 (for example, the reduction voltage) is applied to the thirdelectrode 202 and the fourth electrode 204, the second voltage V2 (forexample, the oxidation voltage) is applied to the first electrode 102and the second electrode 104, and the third voltage V3 (for example, thezero voltage) is applied to the first auxiliary counter electrode 106and the second auxiliary counter electrode 206. In this case, since thethird electrode 202 and the fourth electrode 204 are at the reductionpotential, the first electrode 102 and the second electrode 104 are atthe oxidation potential, and the first auxiliary counter electrode 106and the second auxiliary counter electrode 206 are in an open circuitstate, electric currents (as indicated by arrows) flow from the thirdelectrode 202 and the fourth electrode 204 to the first electrode 102and the second electrode 104. As such, the first electrochromic material112 and the second electrochromic material 114 are colored to be blue(B), and the third electrochromic material 212 and the fourthelectrochromic material 214 are decolored to be transparent (T).Therefore, in this case the pixel unit presents blue when viewed fromthe top or the bottom of the pixel unit.

Referring to FIG. 11, if the pixel unit is to display green, the firstvoltage V1 (for example, the reduction voltage) is applied to the firstelectrode 102 and the second electrode 104, the second voltage V2 (forexample, the oxidation voltage) is applied to the first auxiliarycounter electrode 106, and the third voltage V3 (for example, the zerovoltage) is applied to the third electrode 202, the fourth electrode204, and the second auxiliary counter electrode 206. In this case, sincethe first electrode 102 and the second electrode 104 are at thereduction potential, the first auxiliary counter electrode 106 is at theoxidation potential, and the third electrode 202, the fourth electrode204, and the second auxiliary counter electrode 206 are in an opencircuit state, electric currents (as indicated by arrows) flow from thefirst electrode 102 and the second electrode 104 to the first auxiliarycounter electrode 106. As such, the first electrochromic material 112and the second electrochromic material 114 are colored to be green (G),and the third electrochromic material 212 and the fourth electrochromicmaterial 214 are decolored to be transparent (T). Therefore, in thiscase the pixel unit presents green when viewed from the top or thebottom of the pixel unit.

Referring to FIG. 12, if the pixel unit is to display red, the firstvoltage V1 (for example, the reduction voltage) is applied to the firstauxiliary counter electrode 106, the second voltage V2 (for example, theoxidation voltage) is applied to the third electrode 202 and the fourthelectrode 204, and the third voltage V3 (for example, the zero voltage)is applied to the first electrode 102, the second electrode 104, and thesecond auxiliary counter electrode 206. In this case, since the firstauxiliary counter electrode 106 is at the reduction potential, the thirdelectrode 202 and the fourth electrode 204 are at the oxidationpotential, and the first electrode 102, the second electrode 104, andthe second auxiliary counter electrode 206 are in an open circuit state,electric currents (as indicated by arrows) flow from the first auxiliarycounter electrode 106 to the third electrode 202 and the fourthelectrode 204. As such, the first electrochromic material 112 and thesecond electrochromic material 114 are decolored to be transparent (T),and the third electrochromic material 212 and the fourth electrochromicmaterial 214 are colored to be red (R). Therefore, in this case thepixel unit presents red when viewed from the top or the bottom of thepixel unit.

Referring to FIG. 13, if the pixel unit is to display cyan, the firstvoltage V1 (for example, the reduction voltage) is applied to the firstelectrode 102, the second voltage V2 (for example, the oxidationvoltage) is applied to the second electrode 104, and the third voltageV3 (for example, the zero voltage) is applied to the third electrode202, the fourth electrode 204, the first auxiliary counter electrode106, and the second auxiliary counter electrode 206. In this case, sincethe first electrode 102 is at the reduction potential, the secondelectrode 104 is at the oxidation potential, and the third electrode202, the fourth electrode 204, the first auxiliary counter electrode106, and the second auxiliary counter electrode 206 are in an opencircuit state, electric currents (as indicated by arrows) flow from thefirst electrode 102 to the second electrode 104. As such, the firstelectrochromic material 112 is colored to be green (G), the secondelectrochromic material 114 is colored to be blue (B), and the thirdelectrochromic material 212 and the fourth electrochromic material 214are decolored to be transparent (T). Therefore, in this case the pixelunit presents cyan when viewed from the top or the bottom of the pixelunit.

Referring to FIG. 14, if the pixel unit is to display magenta, the firstvoltage V1 (for example, the reduction voltage) is applied to the firstauxiliary counter electrode 106 and the second auxiliary counterelectrode 206, the second voltage V2 (for example, the oxidationvoltage) is applied to the second electrode 104 and the third electrode202, and the third voltage V3 (for example, the zero voltage) is appliedto the first electrode 102 and the fourth electrode 204. In this case,since the first auxiliary counter electrode 106 and the second auxiliarycounter electrode 206 are at the reduction potential, the secondelectrode 104 and the third electrode 202 are at the oxidationpotential, and the first electrode 102 and the fourth electrode 204 arein an open circuit state, electric currents (as indicated by arrows)flow from the first auxiliary counter electrode 106 to the secondelectrode 104, and flow from the second auxiliary counter electrode 206to the third electrode 202. As such, the second electrochromic material114 is colored to be blue (B), the third electrochromic material 212 iscolored to be red (R), and the first electrochromic material 112 and thefourth electrochromic material 214 are decolored to be transparent (T).Therefore, in this case the pixel unit presents magenta when viewed fromthe top or the bottom of the pixel unit.

Referring to FIG. 15, if the pixel unit is to display yellow, the firstvoltage V1 (for example, the reduction voltage) is applied to the firstelectrode 102, the second voltage V2 (for example, the oxidationvoltage) is applied to the fourth electrode 204, and the third voltageV3 (for example, the zero voltage) is applied to the second electrode104, the third electrode 202, the first auxiliary counter electrode 106,and the second auxiliary counter electrode 206. In this case, since thefirst electrode 102 is at the reduction potential, the fourth electrode204 is at the oxidation potential, and the second electrode 104, thethird electrode 202, the first auxiliary counter electrode 106, and thesecond auxiliary counter electrode 206 are in an open circuit state, anelectric current (as indicated by arrows) flows from the first electrode102 to the fourth electrode 204. As such, the first electrochromicmaterial 112 is colored to be green (G), the fourth electrochromicmaterial 214 is colored to be red (R), and the second electrochromicmaterial 114 and the third electrochromic material 212 are decolored tobe transparent (T). Therefore, in this case the pixel unit presentsyellow when viewed from the top or the bottom of the pixel unit.

Based on the above, according to this disclosure, the plurality ofelectrochromic materials are disposed in the single pixel unit, and thusthe pixel unit may present black, white, or other colors by switchingthe voltages of the above electrodes. Compared with the conventionalreflective display, the design of the pixel unit eliminates the problemof decreased reflectivity, and the driving method of the pixel unit issimple.

It will be apparent to those skilled in the art that variousmodifications and variations can be made to the structure of thedisclosed embodiments without departing from the scope or spirit of thedisclosure. In view of the foregoing, it is intended that the disclosurecover modifications and variations of this disclosure provided they fallwithin the scope of the following claims and their equivalents.

1. A pixel unit of an electrochromic display panel, comprising: a firstsubstrate; a first electrode, on the first substrate; a secondelectrode, on the first substrate and electrically insulated from thefirst electrode; a first auxiliary counter electrode, on the firstsubstrate and disposed between the first electrode and the secondelectrode; a first electrochromic material, on the first electrode; asecond electrochromic material, on the second electrode; a secondsubstrate, opposite to the first substrate; a third electrode, on thesecond substrate; a third electrochromic material, on the thirdelectrode; and an electrolyte layer, between the first substrate and thesecond substrate.
 2. The pixel unit of an electrochromic display panelaccording to claim 1, wherein one of the first electrochromic material,the second electrochromic material, and the third electrochromicmaterial is a monochromatic-transparent electrochromic material, and theother two are a dichromatic-transparent electrochromic material.
 3. Thepixel unit of an electrochromic display panel according to claim 2,wherein the monochromatic-transparent electrochromic material isselected from a blue-transparent (B-T) electrochromic material, agreen-transparent (G-T) electrochromic material, or a red-transparent(R-T) electrochromic material.
 4. The pixel unit of an electrochromicdisplay panel according to claim 2, wherein the dichromatic-transparentelectrochromic material is selected from a blue-green-transparent(B-G-T) electrochromic material, a green-red-transparent (G-R-T)electrochromic material, or a red-blue-transparent (R-B-T)electrochromic material.
 5. The pixel unit of an electrochromic displaypanel according to claim 1, wherein the third electrochromic material isabove the first electrochromic material and the second electrochromicmaterial.
 6. The pixel unit of an electrochromic display panel accordingto claim 1, wherein the first electrode and the second electrode arerespectively a reflective electrode, and the third electrode is atransparent electrode.
 7. The pixel unit of an electrochromic displaypanel according to claim 1, wherein the first electrode and the secondelectrode are respectively a transparent electrode, and the thirdelectrode is a reflective electrode.
 8. The pixel unit of anelectrochromic display panel according to claim 1, further comprising: afourth electrode, on the second substrate; a fourth electrochromicmaterial, on the fourth electrode; and a second auxiliary counterelectrode, on the second substrate and disposed between the thirdelectrode and the fourth electrode.
 9. The pixel unit of anelectrochromic display panel according to claim 8, wherein two of thefirst electrochromic material, the second electrochromic material, thethird electrochromic material, and the fourth electrochromic materialare a monochromatic-transparent electrochromic material, and the othertwo are a dichromatic-transparent electrochromic material.
 10. The pixelunit of an electrochromic display panel according to claim 9, whereinthe monochromatic-transparent electrochromic material is selected from aB-T electrochromic material, a G-T electrochromic material, or an R-Telectrochromic material.
 11. The pixel unit of an electrochromic displaypanel according to claim 9, wherein the dichromatic-transparentelectrochromic material is selected from a B-G-T electrochromicmaterial, a G-R-T electrochromic material, or an R-B-T electrochromicmaterial.
 12. The pixel unit of an electrochromic display panelaccording to claim 8, wherein the first electrode and the secondelectrode are respectively a reflective electrode, and the thirdelectrode and the fourth electrode are respectively a transparentelectrode.
 13. The pixel unit of an electrochromic display panelaccording to claim 8, wherein the first electrode and the secondelectrode are respectively a transparent electrode, and the thirdelectrode and the fourth electrode are respectively a reflectiveelectrode.
 14. The pixel unit of an electrochromic display panelaccording to claim 1, wherein one of the first substrate and the secondsubstrate is a reflective substrate.
 15. A driving method of a pixelunit of an electrochromic display panel, for driving the pixel unitaccording to claim 1, the method comprising: when a first voltage isapplied to the first electrode and the second electrode, a secondvoltage is applied to the third electrode, and a third voltage isapplied to the first auxiliary counter electrode, the pixel unitdisplays black; when the first voltage is applied to the thirdelectrode, the second voltage is applied to the first auxiliary counterelectrode, and the third voltage is applied to the first electrode andthe second electrode, the pixel unit displays white; when the firstvoltage is applied to the third electrode, the second voltage is appliedto the first electrode and the second electrode, and the third voltageis applied to the first auxiliary counter electrode, the pixel unitdisplays a first color; when the first voltage is applied to the firstelectrode and the second electrode, the second voltage is applied to thefirst auxiliary counter electrode, and the third voltage is applied tothe third electrode, the pixel unit displays a second color; and whenthe first voltage is applied to the first auxiliary counter electrode,the second voltage is applied to the third electrode, and the thirdvoltage is applied to the first electrode and the second electrode, thepixel unit displays a third color.
 16. The driving method of a pixelunit of an electrochromic display panel according to claim 15, whereinthe first voltage is a reduction voltage, the second voltage is anoxidation voltage, and the third voltage is a zero voltage.
 17. Thedriving method of a pixel unit of an electrochromic display panelaccording to claim 15, wherein the first color, the second color, andthe third color are respectively blue, green, and red.
 18. A drivingmethod of a pixel unit of an electrochromic display panel, for drivingthe pixel unit according to claim 8, the method comprising: when a firstvoltage is applied to the first electrode and the second electrode, asecond voltage is applied to the third electrode and the fourthelectrode, and a third voltage is applied to the first auxiliary counterelectrode and the second auxiliary counter electrode, the pixel unitdisplays black; when the first voltage is applied to the third electrodeand the fourth electrode, the second voltage is applied to the firstauxiliary counter electrode, and the third voltage is applied to thefirst electrode, the second electrode, and the second auxiliary counterelectrode, the pixel unit displays white; when the first voltage isapplied to the third electrode and the fourth electrode, the secondvoltage is applied to the first electrode and the second electrode, andthe third voltage is applied to the first auxiliary counter electrodeand the second auxiliary counter electrode, the pixel unit displays afirst color; when the first voltage is applied to the first electrodeand the second electrode, the second voltage is applied to the firstauxiliary counter electrode, and the third voltage is applied to thethird electrode, the fourth electrode, and the second auxiliary counterelectrode, the pixel unit displays a second color; and when the firstvoltage is applied to the first auxiliary counter electrode, the secondvoltage is applied to the third electrode and the fourth electrode, andthe third voltage is applied to the first electrode, the secondelectrode, and the second auxiliary counter electrode, the pixel unitdisplays a third color.
 19. The driving method of a pixel unit of anelectrochromic display panel according to claim 18, further comprising:when the first voltage is applied to the first electrode, the secondvoltage is applied to the second electrode, and the third voltage isapplied to the third electrode, the fourth electrode, the firstauxiliary counter electrode, and the second auxiliary counter electrode,the pixel unit displays a fourth color; when the first voltage isapplied to the first auxiliary counter electrode and the secondauxiliary counter electrode, the second voltage is applied to the secondelectrode and the third electrode, and the third voltage is applied tothe first electrode and the fourth electrode, the pixel unit displays afifth color; and when the first voltage is applied to the firstelectrode, the second voltage is applied to the fourth electrode, andthe third voltage is applied to the second electrode, the thirdelectrode, the first auxiliary counter electrode, and the secondauxiliary counter electrode, the pixel unit displays a sixth color. 20.The driving method of a pixel unit of an electrochromic display panelaccording to claim 19, wherein the first voltage is a reduction voltage,the second voltage is an oxidation voltage, and the third voltage is azero voltage.
 21. The driving method of a pixel unit of anelectrochromic display panel according to claim 19, wherein the firstcolor, the second color, the third color, the fourth color, the fifthcolor, and the sixth color are respectively blue, green, red, cyan,magenta, and yellow.